Meter Problems

[Robert A. Barker]

All:
I have a 1966 C150 with a Continental 200 engine.
Before I bought the plane,the owner had the generator
removed and replaced with an alternator.Part of that installation included a
circular cluster gage that has a voltmeter,ammeter,cht meter and egt meter.
During my recent run-up I switched the alternator field
off and realized the voltmeter was reading app.3 volts and the ammeter sat
at zero.
Further tests show the voltmeter reads app. 3 volts
when the master is on and zero when the master is off.
I connected a voltmeter to a cigerette lighter plug and it
read 11.9 volts.With the engine running the voltage increases to 14.2.This
shows the alternator is doing it's
thing but the gages are not.Connecting a milliamp meter
across the shunt terminals definately shows a differnt reading when radios
or any lights are turned on or off.
It would appear the meters in the plane have gone west, but it seems too
much of a coincedence that both
would crap out at the same time.Especially since the volt meter reads
something (not correct) while the ammeter
doesn't respond at all.
Anyone had any experience with this sort of thing?My
next step is to cut apart the nice neat wiring harness and try to trace all
wires looking for bad connections or removing the cluster gage and bench
testing.Both of these are a major pain in the a**.I am looking for a simple
solution but I am aware such a thing may exist only in my
sometimes vivid imagination.
Any and all suggestions greatly appreciated.

Bob Barker N8749S

[Stealth Pilot]

On Sun, 3 Apr 2005 09:58:55 -0400, "Robert A. Barker"
> wrote:

> All:
> I have a 1966 C150 with a Continental 200 engine.
>Before I bought the plane,the owner had the generator
>removed and replaced with an alternator.Part of that installation included a
>circular cluster gage that has a voltmeter,ammeter,cht meter and egt meter.
> During my recent run-up I switched the alternator field
>off and realized the voltmeter was reading app.3 volts and the ammeter sat
>at zero.
> Further tests show the voltmeter reads app. 3 volts
>when the master is on and zero when the master is off.
>I connected a voltmeter to a cigerette lighter plug and it
>read 11.9 volts.With the engine running the voltage increases to 14.2.This
>shows the alternator is doing it's
>thing but the gages are not.Connecting a milliamp meter
>across the shunt terminals definately shows a differnt reading when radios
>or any lights are turned on or off.
> It would appear the meters in the plane have gone west, but it seems too
>much of a coincedence that both
>would crap out at the same time.Especially since the volt meter reads
>something (not correct) while the ammeter
>doesn't respond at all.
> Anyone had any experience with this sort of thing?My
>next step is to cut apart the nice neat wiring harness and try to trace all
>wires looking for bad connections or removing the cluster gage and bench
>testing.Both of these are a major pain in the a**.I am looking for a simple
>solution but I am aware such a thing may exist only in my
>sometimes vivid imagination.
> Any and all suggestions greatly appreciated.
>
> Bob Barker N8749S
>
>
the simplest solution would be to mark them unserviceable and keep
flying.
Stealth ( but I bet you wont do that :-) ) Pilot

[John_F]

You most likely have a high resistance in the wiring to one of the
shunt taps. This should be findable with a ohm meter. I will bet it
is a butt splice made with a cheap crimper. Get a T&B IU style
crimping tool.
John

On Sun, 3 Apr 2005 09:58:55 -0400, "Robert A. Barker"
> wrote:

> All:
> I have a 1966 C150 with a Continental 200 engine.
>Before I bought the plane,the owner had the generator
>removed and replaced with an alternator.Part of that installation included a
>circular cluster gage that has a voltmeter,ammeter,cht meter and egt meter.
> During my recent run-up I switched the alternator field
>off and realized the voltmeter was reading app.3 volts and the ammeter sat
>at zero.
> Further tests show the voltmeter reads app. 3 volts
>when the master is on and zero when the master is off.
>I connected a voltmeter to a cigerette lighter plug and it
>read 11.9 volts.With the engine running the voltage increases to 14.2.This
>shows the alternator is doing it's
>thing but the gages are not.Connecting a milliamp meter
>across the shunt terminals definately shows a differnt reading when radios
>or any lights are turned on or off.
> It would appear the meters in the plane have gone west, but it seems too
>much of a coincedence that both
>would crap out at the same time.Especially since the volt meter reads
>something (not correct) while the ammeter
>doesn't respond at all.
> Anyone had any experience with this sort of thing?My
>next step is to cut apart the nice neat wiring harness and try to trace all
>wires looking for bad connections or removing the cluster gage and bench
>testing.Both of these are a major pain in the a**.I am looking for a simple
>solution but I am aware such a thing may exist only in my
>sometimes vivid imagination.
> Any and all suggestions greatly appreciated.
>
> Bob Barker N8749S
>
>